Read calibration based on ranges of program/erase cycles

ABSTRACT

A signal associated with performance of a memory operation can be applied to a memory cell of a first group of memory cells that have undergone PECs within a first range. The signal can have a first magnitude corresponding to a second range of PECs. Whether differences between a first target voltage and the signal and between a second target voltage and the applied signal are at least the threshold value can be determined. Responsive to determining that the differences are at least the threshold value, the first group of memory cells can be associated with a first calibration cluster and the signal having a second magnitude corresponding to a third range of PECs can be applied to a memory cell of a second group of memory cells that have undergone respective quantities of PECs within the second range.

TECHNICAL FIELD

Embodiments of the disclosure relate generally to memory systems andmore specifically relate to read calibration of a memory device based onranges of program/erase cycles (PECs).

BACKGROUND

A memory system can include one or more memory devices that store data.The memory devices can be, for example, non-volatile memory devices andvolatile memory devices. In general, a host system can utilize a memorysub-system to store data at the memory devices and to retrieve data fromthe memory devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be understood more fully from the detaileddescription given below and from the accompanying drawings of variousembodiments of the disclosure. The drawings, however, should not betaken to limit the disclosure to the specific embodiments, but are forexplanation and understanding only.

FIG. 1 illustrates an example computing system that includes a memorysub-system in accordance with some embodiments of the presentdisclosure.

FIG. 2 illustrates an example of a partition including a cyclic bufferportion and a snapshot portion within a memory device in accordance withsome embodiments of the present disclosure.

FIG. 3 illustrates a relationship between quantities of PECs undergoneby groups of memory cells of a memory device and wear leveling windows.

FIG. 4 illustrates different read windows in accordance with someembodiments of the present disclosure.

FIG. 5 is a pictorial representation of an example calibration of anon-volatile memory device in accordance with some embodiments of thepresent disclosure.

FIG. 6 is a flow diagram of an example method for calibration of amemory device in accordance with some embodiments of the presentdisclosure.

FIG. 7 illustrates an example of a system including a computing systemin a vehicle in accordance with some embodiments of the presentdisclosure.

FIG. 8 is a block diagram of an example computer system in whichembodiments of the present disclosure can operate.

DETAILED DESCRIPTION

A memory sub-system can be a storage device, a memory module, or ahybrid of a storage device and memory module. Examples of storagedevices and memory modules are described below in conjunction withFIG. 1. In general, a host system can utilize a memory sub-system thatincludes one or more memory devices, such as memory devices that storedata. The host system can provide data to be stored at the memorysub-system and can request data to be retrieved from the memorysub-system.

Aspects of the present disclosure are directed to read calibration of amemory device based on program/erase cycles (PECs) that the memorydevice has undergone. The memory device can be operated using differenttrims corresponding to different quantities and/or ranges of PECs. Asused herein, a “trim” or “trim set” generally refers to a set ofparameters, such as magnitudes of voltages, differentials, currents,etc. that can be applied to a memory device (via word line and/or bitlines, for example) to operate the memory device (control access to datawritten to the memory device, for example). A media managementoperation, such as a wear leveling operation can be performed inresponse to memory cells undergoing particular quantities of PECs, whichcan be referred to as a wear leveling window. For example, wear levelingcan be performed on a group of memory cells at a wear leveling window of50,000 PECs (50,000 PECs; 100,000 PECs; 150,000 PECs; etc.) undergone bythe group of memory cells.

Some approaches rely on performing such media management operationsbased on solely on characteristics associated with a particular wearleveling window. However, trims with which the group of memory cells isoperated (e.g., programmed) can be changed (modulated) at a differentfrequency than the wear leveling windows. For example, trims can bechanged every 10,000 PECs (10,000 PECs; 20,000 PECs; 30,000 PECs; etc.)undergone by the group of memory cells. Thus, memory cells of a memorydevice can be operated with multiple trims within a wear levelingwindow.

Aspects of the present disclosure address the above and otherdeficiencies by performing a media management operation on memory cellsof a memory device based on a quantity of PECs that the memory cellshave undergone. Based on the result of the media management operation,groups of memory cells can be associated with read levels. For example,by calibrating one or more groups of memory cells of a memory devicethat have undergone same or similar quantities of PECs challengesassociated with disconnects between wear leveling windows and modulationof trims can be mitigated.

FIG. 1 illustrates an example computing system 100 that includes amemory sub-system 104 in accordance with some embodiments of the presentdisclosure. The memory sub-system 104 can include media, such as one ormore volatile memory devices (e.g., memory device 114), one or morenon-volatile memory devices (e.g., memory device 116), or a combinationof such.

A memory sub-system 104 can be a storage device, a memory module, or ahybrid of a storage device and memory module. Examples of a storagedevice include a solid state drive (SSD), a flash drive, a universalserial bus (USB) flash drive, an embedded Multi-Media Controller (eMMC)drive, a Universal Flash Storage (UFS) drive, a secure digital (SD)card, and a hard disk drive (HDD). Examples of memory modules include adual in-line memory module (DIMM), a small outline DIMM (SO-DIMM), andvarious types of non-volatile dual in-line memory modules (NVDIMMs).

The computing system 100 can be a desktop computer, laptop computer,network server, mobile device, a vehicle (e.g., airplane, drone, train,automobile, or other conveyance), Internet of Things (IoT) enableddevice, embedded computer (e.g., one included in a vehicle, industrialequipment, or a networked commercial device), such computing device thatincludes memory and a processing device.

The computing system 100 includes a host system 102 that is coupled toone or more memory sub-systems 104. In some embodiments, the host system102 is coupled to different types of memory sub-systems 104. FIG. 1illustrates one example of a host system 102 coupled to one memorysub-system 104. As used herein, “coupled to” or “coupled with” generallyrefers to a connection between components, which can be an indirectcommunicative connection or direct communicative connection (e.g.,without intervening components), whether wired or wireless, includingconnections such as electrical, optical, magnetic, and the like. In atleast one embodiment, the host system 102 is a computing device thatcontrols a vehicle, such as an autonomous vehicle, and the memorysub-system 104 is an SSD that provides event recorder storage for thevehicle. An event recorder can also be referred to as a “black box” oraccident data recorder. The memory sub-system 104 can store time basedtelemetric sensor data for the vehicle; however, embodiments are notlimited to this example.

The host system 102 can include a processor chipset and a software stackexecuted by the processor chipset. The processor chipset can include oneor more cores, one or more caches, a memory controller (e.g., an SSDcontroller, NVDIMM controller, etc.), and a storage protocol controller(e.g., PCIe controller, SATA controller, etc.). The host system 102 usesthe memory sub-system 104, for example, to write data to the memorysub-system 104 and read data from the memory sub-system 104.

The host system 102 can be coupled to the memory sub-system 104 via aphysical host interface. Examples of a physical host interface include,but are not limited to, a serial advanced technology attachment (SATA)interface, a PCIe interface, universal serial bus (USB) interface, FibreChannel, Serial Attached SCSI (SAS), Small Computer System Interface(SCSI), a double data rate (DDR) memory bus, a dual in-line memorymodule (DIMM) interface (e.g., DIMM socket interface that supportsDouble Data Rate (DDR)), Open NAND Flash Interface (ONFI), Double DataRate (DDR), Low Power Double Data Rate (LPDDR), or any other interface.The physical host interface can be used to transmit data between thehost system 102 and the memory sub-system 104. The host system 102 canfurther utilize an NVM Express (NVMe) interface to access thenon-volatile memory device 116 when the memory sub-system 104 is coupledwith the host system 102 by the PCIe interface. The physical hostinterface can provide an interface for passing control, address, data,and other signals between the memory sub-system 104 and the host system102. FIG. 1 illustrates a memory sub-system 104 as an example. Ingeneral, the host system 102 can access multiple memory sub-systems viaa same communication connection, multiple separate communicationconnections, and/or a combination of communication connections.

The memory devices 114 and 116 can include any combination of thedifferent types of non-volatile memory devices and/or volatile memorydevices. The volatile memory devices (e.g., memory device 114) can be,but are not limited to, random access memory (RAM), such as dynamicrandom-access memory (DRAM) and synchronous dynamic random access memory(SDRAM).

Some examples of non-volatile memory devices (e.g., memory device 116)include negative-and (NAND) type flash memory and write-in-place memory,such as three-dimensional cross-point memory device, which is across-point array of non-volatile memory cells. A cross-point array ofnon-volatile memory can perform bit storage based on a change of bulkresistance, in conjunction with a stackable cross-gridded data accessarray. Additionally, in contrast to many flash-based memories,cross-point non-volatile memory can perform a write in-place operation,where a non-volatile memory cell can be programmed without thenon-volatile memory cell being previously erased. NAND type flash memoryincludes, for example, two-dimensional NAND (2D NAND) andthree-dimensional NAND (3D NAND).

Each of the memory devices 114 and 116 can include one or more arrays ofmemory cells. One type of memory cell, for example, single level cells(SLC) can store one bit per cell. Other types of memory cells, such asmulti-level cells (MLCs), triple level cells (TLCs), quad-level cells(QLCs), and penta-level cells (PLC) can store multiple bits per cell. Insome embodiments, each of the memory devices 116 can include one or morearrays of memory cells such as SLCs, MLCs, TLCs, QLCs, or anycombination of such. In some embodiments, a particular memory device caninclude an SLC portion, and an MLC portion, a TLC portion, a QLCportion, or a PLC portion of memory cells. The memory cells of thememory devices 116 can be grouped as pages that can refer to a logicalunit of the memory device used to store data. With some types of memory(e.g., NAND), pages can be grouped to form blocks.

Although non-volatile memory components such as three-dimensionalcross-point arrays of non-volatile memory cells and NAND type memory(e.g., 2D NAND, 3D NAND) are described, the memory device 130 can bebased on any other type of non-volatile memory or storage device, suchas such as, read-only memory (ROM), phase change memory (PCM),self-selecting memory, other chalcogenide based memories, ferroelectrictransistor random-access memory (FeTRAM), ferroelectric random accessmemory (FeRAM), magneto random access memory (MRAM), Spin TransferTorque (STT)-MRAM, conductive bridging RAM (CBRAM), resistive randomaccess memory (RRAMM), oxide based RRAM (OxRAM), negative-or (NOR) flashmemory, and electrically erasable programmable read-only memory(EEPROM).

The memory sub-system controller 106 (or controller 106 for simplicity)can communicate with the non-volatile memory devices 116 to performoperations such as reading data, writing data, erasing data, and othersuch operations. The memory sub-system controller 106 can includehardware such as one or more integrated circuits and/or discretecomponents, a buffer memory, or a combination thereof. The hardware caninclude digital circuitry with dedicated (i.e., hard-coded) logic toperform the operations described herein. The memory sub-systemcontroller 106 can be a microcontroller, special purpose logic circuitry(e.g., a field programmable gate array (FPGA), an application specificintegrated circuit (ASIC), etc.), or other suitable circuitry.

The memory sub-system controller 106 can include a processor 108 (e.g.,a processing device) configured to execute instructions stored in localmemory 110. In the illustrated example, the local memory 110 of thememory sub-system controller 106 is an embedded memory configured tostore instructions for performing various processes, operations, logicflows, and routines that control operation of the memory sub-system 104,including handling communications between the memory sub-system 104 andthe host system 102.

In some embodiments, the local memory 110 can include memory registersstoring memory pointers, fetched data, etc. The local memory 110 canalso include ROM for storing micro-code, for example. While the examplememory sub-system 104 in FIG. 1 has been illustrated as including thememory sub-system controller 106, in another embodiment of the presentdisclosure, a memory sub-system 104 does not include a memory sub-systemcontroller 106, and can instead rely upon external control (e.g.,provided by an external host, or by a processor or controller separatefrom the memory sub-system 104).

In general, the memory sub-system controller 106 can receive informationor operations from the host system 102 and can convert the informationor operations into instructions or appropriate information to achievethe desired access to the non-volatile memory device 116 and/or thevolatile memory device 114. The memory sub-system controller 106 can beresponsible for other operations such as wear leveling operations, errordetection and/or correction operations, encryption operations, cachingoperations, and address translations between a logical address (e.g.,logical block address (LBA)) and a physical address (e.g., physicalblock address (PBA)) associated with the non-volatile memory device 116.The memory sub-system controller 106 can further include host interfacecircuitry to communicate with the host system 102 via the physical hostinterface. The host interface circuitry can convert a query receivedfrom the host system 102 into a command to access the non-volatilememory device 116 and/or the volatile memory device 114 as well asconvert responses associated with the non-volatile memory device 116and/or the volatile memory device 114 into information for the hostsystem 102.

The host system 102 can send requests to the memory sub-system 104, forexample, to store data in the memory sub-system 104 or to read data fromthe memory sub-system 104. The data to be written or read, as specifiedby a host request, is referred to as “host data.” A host request caninclude logical address information. The logical address information canbe an LBA, which can include or be accompanied by a partition number.The logical address information is the location the host systemassociates with the host data. The logical address information can bepart of metadata for the host data. The LBA can also correspond (e.g.,dynamically map) to a physical address, such as a PBA, that indicatesthe physical location where the host data is stored in memory.

The memory sub-system 104 can also include additional circuitry orcomponents that are not illustrated. In some embodiments, the memorysub-system 104 can include a cache or buffer (e.g., DRAM) and addresscircuitry (e.g., a row decoder and a column decoder) that can receive anaddress from the memory sub-system controller 106 and decode the addressto access the memory device 114 and/or the memory device 116.

In some embodiments, the memory device 116 includes a local mediacontroller 118 that operates in conjunction with memory sub-systemcontroller 106 to execute operations on one or more memory cells of thenon-volatile memory device 116. An external controller (e.g., memorysub-system controller 106) can externally manage the memory device 116(e.g., perform media management operations on the memory device 116). Insome embodiments, a memory device 116 is a managed memory device, whichis a raw memory device combined with a local controller (e.g., localcontroller 118) for media management within the same memory devicepackage. An example of a managed memory device is a managed NAND device.

In some embodiments, the memory sub-system controller 118 includes atleast a portion of the calibration circuitry 112. For example, thememory sub-system controller 118 can include a processor 108 (e.g., aprocessing device) configured to execute instructions stored in localmemory 110 for performing the operations described herein. In someembodiments, the calibration circuitry 112 is part of the host system102, an application, or an operating system.

In some embodiments, the calibration circuitry 112 can issue, or causeto be issued, a set trim command, which causes the memory device 116 (orportions thereof, such as logical units) to use a particular set ofoperating parameters to operate the memory cells of the memory device116. Trims can include operating parameters associated with variousoperations such as program (write), program verify, erase, erase verify,and sense (read), among other operations associated with memory cells.

Trims can be used to achieve or adjust desired target voltages forprogramming memory cells, which can create different threshold voltage(V_(t)) distributions for data states. Trims can be used to achieve aread window or adjust a read window between data states (e.g., thevoltage spread between different V_(t) distributions for different datastates for memory cells of the memory device 116). Different trims canbe used for different operations such as programming, reading, and/orerasing.

Examples of trims include programming voltages, programming frequency, aprogram start voltage, a program step voltage, a program inhibit startvoltage, and an erase verify voltage. The program start voltage is themagnitude of an initial programming voltage pulse of a series of voltagepulses applied to a selected word line during a programming operationperformed on memory cells in a selected block. The program step voltageis the voltage step size between programming voltage pulses. The programinhibit start voltage is a voltage used to inhibit further programmingof memory cells once the V_(t) associated with a desired data state hasbeen reached. The erase verify voltage is the voltage used to checkwhether memory cells in the selected block have a V_(t) indicative ofthe erase state.

Other examples of trims include read reference voltages and/or programverify voltages. Program verify voltages represent target voltage levelsto which memory cells are to be programmed in order to represent aparticular data state. Read reference voltages are voltage levels thatcan be located between program V_(t) distributions and used to determinea particular data state of a data cell during a data read operation. Asused herein, trims are distinguished from programming times. Thefollowing description of some example functionality of the calibrationcircuitry 112 is described in association with FIG. 5.

Groups of memory cells of the non-volatile memory device 116 can undergodifferent quantities of PECs throughout the service life of thenon-volatile memory device 116. A group of memory cells can be aphysical block of memory cells. The calibration circuitry 112 can beconfigured to perform a media management operation on a group of memorycells of the non-volatile memory device 116 that has undergone variousquantities of PECs. A magnitude of a signal (e.g., a magnitude of a readvoltage) this is applied to the group of memory cells during the mediamanagement operation can be based on in which range of PECs (e.g., 0 to10,000 PECs, 10,001 to 20,000 PECs, etc.) that the quantities of PECsundergone by the group of memory cells lie. The magnitude of the signalcan correspond to a different range of PECs that exceeds the range ofPECs undergone by the group of memory cells. For example, if the groupof memory cells has undergone no more than 10,000 PECs (within the rangeof 0 to 10,000 PECs), then the magnitude of the signal can correspond toa range of PECs exceeding 10,000 PECs (e.g., 10,001 to 20,000 PECs).

In response to a successful result of the media management operation,the media management operation can be performed on a different group ofmemory cells of the non-volatile memory device 116 that has undergone aquantity of PECs within a range of PECs that exceeds the range of PECsundergone by the previous group of memory cells (e.g., 10,001 to 20,000PECs). A magnitude of the signal with which the media managementoperation is performed on the other group of memory cells can correspondto a range of PECs exceeding the range of PECs of the other group ofmemory cells (e.g., 20,001 to 30,000 PECs). In response to anunsuccessful result of the media management operation on the group ofmemory cells, the media management operation can be performed on theother group of memory cells using a voltage of the same magnitude withwhich the media management operation was performed on the group ofmemory cells.

The calibration circuitry 112 can be configured to, in response to asuccessful result of performing the media management operation on thedifferent group of memory cells, perform the media management operationon another group of memory cells of the non-volatile memory device 116that has undergone a quantity of PECs within the range of PECs of thedifferent group of memory cells. A magnitude of the signal with whichthe media management operation is performed can correspond to a range ofPECs exceeding the range of PECs of the other group of memory cells(e.g., 30,001 to 40,000 PECs). The calibration circuitry 112 can beconfigured to, in response to an unsuccessful result of the mediamanagement operation, perform the media management operation on theother group of memory cells. A magnitude of the signal with which themedia management operation is performed can be the same magnitude aswith which the media management operation was performed on the differentgroup of memory cells.

The calibration circuitry 112 can execute instructions to utilizedifferent trims on different groups of memory cells where the trims arebased on a quantity of PECs undergone by a respective group of memorycells. For example, the calibration circuitry 112 can executeinstructions to selectively vary a magnitude of a target voltagecorresponding to a particular data state based on a quantity of PECsthat the non-volatile memory device 116 has undergone. The calibrationcircuitry 112 can execute instructions to, throughout a service life ofthe non-volatile memory device 116, increase a read window of one ormore memory cells of the non-volatile memory device 116 based on thequantity of PECs that the non-volatile memory device 116 has undergone.A magnitude of a target voltage corresponding to a different data statecan be static throughout the service life of the non-volatile memorydevice 116. The magnitude of the target voltage corresponding to theparticular data state can be dynamic such that the magnitude of thetarget voltage is increased based on the quantity of PECs that thememory device has undergone. The calibration circuitry 112 can executeinstructions to program one or more memory cells of the non-volatilememory device 116 such that one or more memory cells of the non-volatilememory device 116 remains at a V_(t) corresponding to an erased state,and one or more memory cells of the memory device is programmed to adifferent V_(t) corresponding to a programmed state. A magnitude of thedifferent V_(t) can be increased, over the service life of thenon-volatile memory device 116, based on the quantity of PECs that thenon-volatile memory device 116 has undergone.

In at least one embodiment of the present disclosure, the non-volatilememory device 116 can include a cyclic buffer portion (e.g., the cyclicbuffer portion 222 illustrated by FIG. 2) and a snapshot portion (e.g.,the snapshot portion 224 illustrated by FIG. 2). The calibrationcircuitry 112 can execute instructions to utilize different trims withdifferent groups of memory cells of the snapshot potion based on aquantity of PECs.

FIG. 2 illustrates an example of a partition 220 including a cyclicbuffer portion 222 and a snapshot portion 224 within a memory device 216in accordance with some embodiments of the present disclosure. Thecyclic buffer portion 222 and snapshot portion 224 can be reservedportions of the partition 220. Host data can be received by the memorysub-system. The host data can be time based telemetric sensor data fromdifferent sensors of a vehicle. The time based telemetric sensor datafrom the different sensors can be aggregated by the host and sent to thememory sub-system at a data rate. The host data can be received by thememory sub-system and stored in the cyclic buffer portion 222 of thenon-volatile memory device 216. As the cyclic buffer portion 222 isfilled with host data, new data received from the host is storedsequentially, but older data in the cyclic buffer portion 222 can beerased or overwritten. The cyclic buffer portion 222 can thereforeoperate as a first-in-first-out (FIFO) buffer, where newly received datareplaced the oldest data therein.

The cyclic buffer portion 222 can be coupled to the snapshot portion224. Upon occurrence of a trigger event 226, an amount of the time basedtelemetric sensor data from the cyclic buffer portion 222 can be copiedto the snapshot portion 224. The recorded telemetric sensor datacorresponding to the predetermined playback time can be referred to as a“snapshot”. The amount of host data corresponding to a defined period oftime, which may be referred to as a playback time (e.g., 30 seconds), isreferred to as a snapshot size whereas the data itself over that definedperiod of time is referred to as a snapshot. The snapshot size can bepredefined for a period of time immediately preceding a trigger event.The snapshot size and/or playback time can be a predefined valueprogrammed to the memory sub-system by a manufacturer, supplier, or userof the memory sub-system. In some embodiments, the determination thatthe trigger event 226 has occurred can include actuation of a triggersignal based at least in part upon received sensor information from ahost that is above a threshold, such as a quantitative value.

The cyclic buffer portion 222 can store significantly more data over theservice life of the memory device 216 than the snapshot portion 224. Forexample, the cyclic buffer portion 222 can store 3-4 orders of magnitude(1,000-10,000 times) more data than the snapshot portion 224. However,the cyclic buffer portion 222 does not have a greater storage capacitythan the snapshot portion 224. Rather, the size (amount of memory) ofthe snapshot portion 224 can be based on the rate at which data is to bereceived from the host, a playback time, and a quantity of snapshotsthat are desired to be available in the snapshot portion 224. Thesnapshot portion 224 can have sufficient storage to save [data rate fromhost (e.g., in GB/sec) * playback time (e.g., in sec) * desired quantityof snapshots (e.g., a whole number)]. In other words, the size of thesnapshot portion 224 can be sufficiently large to store a desired numberof snapshots. As used herein, the size of the snapshot portion 224 isreferred to as “a user capacity” of the memory sub-system.

The memory sub-system can be configured to operate the snapshot portion224 such that memory cells of the snapshot portion 224 are programmed toa V_(t) based on a remaining service life of the memory sub-system. Itis desirable for the snapshot portion 224 to store data accurately andreliably because the snapshots are intended to be recoverable after atrigger event. Thus, a performance target of the snapshot portion 224can be data retention. However, embodiments of the present disclosureare not so limited. For example, the memory sub-system can be configuredto operate the cyclic buffer portion 222 such that memory cells of thecyclic buffer portion 222 are programmed to a V_(t) based on a remainingservice life of the memory sub-system. It is desirable for the cyclicbuffer portion 222 to store data accurately and reliably because thecyclic buffer portion 222 is used repeatedly and frequently (in someembodiments, significantly more frequently than the snapshot portion224). Thus, a performance target of the cyclic buffer portion 222 can bedata retention.

The copying of a snapshot from the cyclic buffer portion 222 to thesnapshot portion 224 can be powered by a power supply 228 of the memorysub-system under normal circumstances. However, copying of the snapshotfrom the cyclic buffer portion 222 to the snapshot portion 224 can bepowered by a backup power supply, such as one or more hold-up capacitors230 in response to a loss of system power (e.g., the power supply 228),which can be associated with the trigger event 226, such as a vehicleaccident. In at least one embodiment, the loss of power from the powersupply 228 can be the trigger event 226. A size and/or quantity of thehold-up capacitor(s) 230 are sufficient to provide enough power to copyone snapshot from the cyclic buffer portion 222 to the snapshot portion224. As illustrated, the power supply 228 and the hold-up capacitor 230are coupled to the cyclic buffer portion 222 and the snapshot portion224. This indicates that the power supply 228 and the hold-up capacitor230 are coupled to the memory device 216 to provide power therefor.There may not be a direct physical connection between either the powersupply 228 or the hold-up capacitor 230 and the partition 220, but thepower can be provided through write circuitry (not specificallyillustrated).

In some embodiments, memory cells of the cyclic buffer portion 222 canbe operated so as to store one bit per cell (SLC mode) and memory cellsof the snapshot portion 224 can be operated so as to store more than onebit per cell. It can take longer to operate memory cells that store morethan one bit per cell than to operate memory cells that store only onebit per cell. For example, an increased number of data statesrepresented by the memory cells having multiple bits per cell canfurther increase complexity of an algorithm associated with programming,reading, and/or erasing the memory cells. Therefore, the memory cellsprogrammed to store multiple bits per cell can have a differentprogramming characteristic, such as a slower data transfer rate and/orlonger programming time (e.g., time elapsed to program data to thememory cells), than that of the SLC memory cells and/or memory cellsprogrammed to store fewer bits per cell. Memory cells of the cyclicbuffer portion 222 can be operated with a faster programming time than aprogramming time for the memory cells of the snapshot portion 224.

FIG. 3 illustrates a relationship between quantities of PECs undergoneby groups of memory cells of a memory device and wear leveling windows331-1, 331-2, and 331-3. Each of the rectangles 333-1, 333-2, 333-3,333-4, 333-5, and 333-6 represents a range of PECs. For example, therectangle 333-1 can represent 0 to 10,000 PECs, the rectangle 333-2 canrepresent 10,001 to 20,000 PECs, the rectangle 333-3 can represent20,001 to 30,000 PECs, the rectangle 333-4 can represent 30,001 to40,000 PECs, the rectangle 333-5 can represent 40,001 to 50,000 PECs,and the rectangle 333-6 can represent 50,001 to 60,000 PECs. In at leastone embodiment, trims used to perform programming operations, forexample, on respective groups of memory cells of the memory device canbe based on a quantity of PECs that each respective group of memorycells has undergone. For instance, if a group of memory cells hasundergone no more than 10,000 PECs (represented by the rectangle 333-2),then trims used to program the group of memory cells can correspond tothe range of 0 to 9,999 PECs. If a group of memory cells has undergoneno more than 20,000 PECs but at least 10,001 PECs (represented by therectangle 333-3), then trims used to program the group of memory cellscan correspond to the range of 10,001 to 20,000 PECs.

The vertical, dashed lines 329-1, 329-2, and 329-3 represent boundariesof the wear leveling windows 331-1, 331-2, and 331-3. Wear levelingwindows can span a different range of PECs than the ranges of PECs onwhich trims are based. For example, trims can be based on ranges of PECsthat span 10,000 PECs whereas wear leveling windows can span a range of100,000 PECs. As illustrated by FIG. 3, ranges of PECs on which trimselection can be based are within different wear leveling windows. Forexample, the rectangle 333-2, representing the range of 10,001 to 20,000PECs, is in the wear leveling window 331-1 and the rectangle 333-3,representing the range of 20,001 to 30,000 PECs, is in the wear levelingwindow 331-2. Thus, different groups of memory cells programed usingdifferent trims (e.g., have different read windows as described inassociation with FIG. 4) can be within different wear leveling windows.However, as illustrated by FIG. 3, different groups of memory cells canundergo quantities of PECs within different ranges of PECs, and thus beprogramed using different trims, but be within the same wear levelingwindow. For example, the rectangle 333-3, representing the range of20,001 to 30,000 PECs, and the rectangle 333-4, representing the rangeof 30,001 to 40,000 PECs, are both within the wear leveling window331-2.

Because there can be a disconnect between trims which groups of memorycells of a memory device are operated and the granularity of wearleveling windows, calibration of the memory device can be difficult tomaintain and difficult to perform on the memory device all at once.Embodiments of the present disclosure overcome this difficulty andimprove calibration of a memory device by accounting for the varioustrims with which groups of memory cells of the memory device areprogramed. At least one embodiment includes calibrating groups of memorycells that have undergone quantities of PECs within a same range ofPECs.

FIG. 4 illustrates different read windows 432-1, 432-2, and 432-3 inaccordance with some embodiments of the present disclosure. Thehorizontal axis represents the charge or voltage of the memory cell(V_(t)) and the vertical axis represents the quantity of memory cellsfor each data state (1 and 0) that are programmed to a particularvoltage. The curves for each data state (1 and 0) therefore representstatistical distributions of memory cell threshold voltages for eachdata state. The read windows 432-1, 432-2, and 432-3 are the respectiveseparation between the V_(t) distributions along the horizontal axis(e.g., in volts). A read window can also be referred to as a read windowbudget (RWB), a threshold voltage (V_(t)) spread, or a valley width. Avalley width refers to a difference in magnitude of different programverify voltages for different programmed states or a program verifyvoltage and an erase verify voltage for different data states.

Memory cells of a non-volatile memory device can be in good conditionearly in the service life of the non-volatile memory device. Because thememory cells are in good condition, large valley margins are notrequired. Thus, the non-volatile memory device can utilize a narrow readwindow, such as the read window 432-1, without negatively affecting thereliability of the non-volatile memory device. Utilizing a narrow readwindow can slow down degradation of memory cells of the non-volatilememory device, which, in turn, can increase the endurance and dataretention performance of the non-volatile memory device.

FIG. 4 provides a graphical representation of programming a group ofmemory cells of a non-volatile memory device to a V_(t) based on aquantity of PECs that the group of memory cells has undergone. Forexample, early in the service life of the non-volatile memory device,memory cells of the non-volatile memory device can be programmed usingtrims resulting in the read window 432-1. The read window 432-1 isnarrow such that the V_(t) distribution associated with a data state(e.g., an erased state (1)) is close to the V_(t) distributionassociated with a different data state (e.g., a programmed state (0)). Anarrower V_(t) spread between data states can reduce the datareliability because it can be more difficult to distinguish between thedata states. But because the memory cells are in good condition early inthe service life of the non-volatile memory device, data states of thememory cells can still be distinguished between even when the readwindow 432-1 is used.

A benefit of using a narrow read window, such as the read window 420-1,early in the service life of the non-volatile memory device can bereducing memory cell degradation early in the service life of thenon-volatile memory device instead of using a wide read window, such asthe read window 432-3, throughout the service life of the non-volatilememory device. Programming a memory cell to a greater V_(t) (andsubsequently erasing the memory cell) over many cycles can degrade thememory cell at a faster rate than programming the memory to a lowerV_(t) (and subsequently erasing the memory) early in the service life ofthe non-volatile memory device and increasing the V_(t) throughout theservice life of the non-volatile memory device in accordance with someembodiments of the present disclosure. Furthermore, although operationof an SLC is generally illustrated in FIG. 4, embodiments are not solimited. The same principles can be applied to memory cells that areoperated with more than one programmed state. For example, embodimentsof the present disclosure can include programming a memory cell in MLCmode, TLC mode, QLC mode, or PLC mode.

As illustrated by FIG. 4, some embodiments of the present disclosureinclude increasing the V_(t) corresponding to the data state 0 as thenon-volatile memory device undergoes more PEC. Programming the memorycells to a greater V_(t) requires a greater voltage and/or increasednumber of voltage pulses to be applied to the memory cells, which candegrade the materials of the memory cells. During the middle of theservice life of the non-volatile memory device, memory cells of thenon-volatile memory device can be programmed to a greater V_(t)corresponding to a desired data state. In response to the non-volatilememory undergoing further PEC, memory cells of the non-volatile memorydevice can be programmed to a greater V_(t) corresponding to the datastate 0 as illustrated by the read window 432-2. During the latterportion of the service life of the non-volatile memory device, memorycells of the non-volatile memory device can be programmed to an evengreater V_(t) corresponding to a desired data state. In response to thenon-volatile memory undergoing even further PEC, memory cells of thenon-volatile memory device can be programmed to an even greater V_(t)corresponding to the data state 0 as illustrated by the read window432-3. Increasing the read window based on the quantity of PEC that thememory device, block, or cell has undergone (for example, from the readwindow 432-1 to the read window 432-2 and/or the read window 432-3) inaccordance with some embodiments of the present disclosure can bebeneficial to improve data retention of the memory device.

Although FIG. 4 illustrates three different read windows 432-1, 432-2,and 432-3, embodiments of the present disclosure are not so limited.FIG. 3 illustrates six ranges of PECs represented by the rectangles 333.Each range of PECs can be associated with different trims that providesix different read windows.

FIG. 5 is a pictorial representation of an example calibration of anon-volatile memory device in accordance with some embodiments of thepresent disclosure. FIG. 5 is described in association with an examplemethod in accordance with some embodiments of the present disclosureillustrated by FIG. 6.

FIG. 6 is a flow diagram of an example method for calibration of amemory device in accordance with some embodiments of the presentdisclosure. The method can be performed by processing logic that caninclude hardware (e.g., processing device, circuitry, dedicated logic,programmable logic, microcode, hardware of a device, integrated circuit,etc.), software (e.g., instructions run or executed on a processingdevice), or a combination thereof. In some embodiments, the method isperformed by or using the memory sub-system controller 106, processingdevice 108, calibration circuitry 112, non-volatile memory device 116and/or volatile memory device 114, and/or local media controller 118shown in FIG. 1. Although shown in a particular sequence or order,unless otherwise specified, the order of the processes can be modified.Thus, the illustrated embodiments should be understood only as examples,and the illustrated processes can be performed in a different order, andsome processes can be performed in parallel. Additionally, one or moreprocesses can be omitted in various embodiments. Thus, not all processesare required in every embodiment. Other process flows are possible.

At operation 670, a signal associated with performance of a memoryoperation and having a first magnitude, can be applied to a memory cellof a first group of memory cells of a memory device. Memory cells of thefirst group have undergone respective quantities of PECs within a firstrange of PECs. FIG. 5 illustrates PEC clusters 537-1, 537-2, 537-3,537-4, 537-5, 537-6, 537-7, 537-8, 537-9, and 537-10. As used herein,“PEC cluster” refers one or more groups of memory cells that haveundergone one or more quantities of PECs with a range of PECs to which aPEC cluster corresponds. In the example of FIG. 5, groups of memorycells that have undergone no more than 10,000 PECs are associated withPEC cluster 537-1. Groups of memory cells that have undergone no morethan 20,000 PECs but at least 10,001 PECs are associated with PECcluster 537-2. Groups of memory cells that have undergone no more than30,000 PECs but at least 20,001 PECs are associated with PEC cluster537-3. Groups of memory cells that have undergone no more than 40,000PECs but at least 30,001 PECS are associated with PEC cluster 537-4.Groups of memory cells that have undergone no more than 50,000 PECs butat least 40,001 PECs are associated with PEC cluster 537-5. Groups ofmemory cells that have undergone no more than 60,000 PECs but at least50,001 PECs are associated with PEC cluster 537-6. Groups of memorycells that have undergone no more than 70,000 PECs but at least 60,001PECs are associated with PEC cluster 537-7. Groups of memory cells thathave undergone no more than 80,000 PECs but at least 70,001 PECs areassociated with PEC cluster 537-8. Groups of memory cells that haveundergone no more than 90,000 PECs but at least 80,001 PECs areassociated with PEC cluster 537-9. Groups of memory cells that haveundergone no more than 100,000 PECs but at least 90,001 PECs areassociated with PEC cluster 537-10.

The first group of memory cells can be associated with the PEC cluster537-1. At block 670, the example method includes the first magnitude ofthe signal corresponding to a second range of PECs that is differentthan the first range of PECs. For example, the second range of PECs canbe the range of 10,001 to 20,000 PECs associated with the PEC cluster537-2.

At operations 671 and 672, a media management operation can be performedon the first group of memory cells. A non-limiting example of a mediamanagement operation is a margin check. As used herein, “margin check”refers to an operation performed on a group of memory cells to verifythat a magnitude of a signal applied to the memory cells satisfies errorhandling requirements of a memory device. The signal can be a readsignal and the magnitude of a read signal can be referred to as a readlevel. A margin check can include performing two static reads usingpredefined read levels. A margin check can include performing two staticreads using predefined offsets from a read level associated with the PECcluster to which the group of memory cells are assigned.

At operation 671, whether a difference between a target voltagecorresponding to a first data state and the applied signal having thefirst magnitude is at least a threshold value can be determined for thefirst group of memory cells. At operation 672, whether a differencebetween a target voltage corresponding to a second data state and theapplied signal having the first magnitude is at least the thresholdvalue can be determined for the first group of memory cells.

At operation 673, in response to determining that both differences areat least the threshold value, the first group of memory cells can beassociated with a first calibration cluster. As used herein,“calibration cluster” refers to one or more groups of memory cells thatutilize a same read level. FIG. 5 illustrates three calibration clusters534, 535, and 536. If a margin check performed on a group of memorycells associated with the PEC cluster 537-1, such as the first group ofmemory cells, based on a read level corresponding to the PEC cluster537-2 is indicative of the differences being at least the thresholdvalue (i.e., a successful margin check), then the PEC cluster 537-1 andthe groups of memory cells associated therewith are associated with thecalibration cluster 534.

At operation 674, in response to determining that both differences areat least the threshold value, the signal having a second magnitude canbe applied to a memory cell of a second group of memory cells of thememory device. Memory cells of the second group have undergonerespective quantities of PECs within the second range of PECs describedin association with block 670. The second magnitude corresponds to athird range of PECs different than the second range of PECs. Forexample, the third range of PECs can be the range of 20,001 to 30,000PECs associated with the PEC cluster 537-3.

Although not specifically illustrated, the method can include,determining, for the second group of memory cells, whether a differencebetween a target voltage corresponding to the first data state and theapplied signal having the second magnitude is at least the thresholdvalue. The method includes determining, for the second group of memorycells, whether a difference between a target voltage corresponding tothe second data state and the applied signal is at least the thresholdvalue. The method can include, in response to determining that bothdifferences are at least the threshold value, associating the secondgroup of memory cells with the first calibration cluster. If a margincheck performed on a group of memory cells associated with the PECcluster 537-2, such as the second group of memory cells, based on a readlevel corresponding to the PEC cluster 537-2 is indicative of thedifferences being at least the threshold value (i.e., a successfulmargin check), then the PEC cluster 537-2 and the groups of memory cellsassociated therewith are associated with the calibration cluster 534 asillustrated by FIG. 5.

The method can further include applying the signal having a thirdmagnitude to a memory cell of a third group of memory cells of thememory device. Memory cells of the third group have undergone respectivequantities of PECs within the third range of PECs. The third magnitudecorresponds to a fourth range of PECs different from the third range ofPECs. For example, the fourth range of PECs can be the range of 30,001to 40,000 PECs associated with the PEC cluster 537-4.

Although not specifically illustrated, the method can include, inresponse to determining, for the first group of memory cells, that oneor both of the differences is less than the threshold value, associatingthe first group of memory cells with a second calibration cluster. Themethod can further include designating the second calibration cluster asa primary calibration cluster. As used herein, “primary calibrationcluster” refers to a calibration cluster to which the read level is usedfor calibration of the memory device. The method can further includedesignating the second calibration cluster as the primary calibrationcluster in response to a greater quantity of groups of memory cells ofthe memory device being associated with the second calibration clusterthan the first calibration cluster. If a same quantity of groups ofmemory cells of the memory device is associated with the first andsecond calibration clusters, then the method can include designating thesecond calibration cluster as the primary calibration cluster inresponse to groups of memory cells of the memory device that haveundergone greater quantities of PECs being associated with the secondcalibration cluster than the first calibration cluster.

In the example illustrated by FIG. 5, a margin check is performed onmemory cells associated with the PEC cluster 537-1 using a read levelcorresponding to the PEC cluster 537-2. Because the margin check wassuccessful, the PEC cluster 537-1, and groups of memory cells associatedtherewith, are associated with the calibration cluster 534.Subsequently, a margin check is performed on memory cells associatedwith the PEC cluster 537-2 using a read level corresponding to the PECcluster 537-3. Because the margin check was successful, the PEC cluster537-2, and groups of memory cells associated therewith, are associatedwith the calibration cluster 534. Subsequently, a margin check isperformed on memory cells associated with the PEC cluster 537-3 using aread level corresponding to the PEC cluster 537-4. Because the margincheck was successful, the PEC cluster 537-3, and groups of memory cellsassociated therewith, are associated with the calibration cluster 534.Subsequently, a margin check is performed on memory cells associatedwith the PEC cluster 537-4 using a read level corresponding to the PECcluster 537-5. Because the margin check was successful, the PEC cluster537-4, and groups of memory cells associated therewith, are associatedwith the calibration cluster 534.

A margin check is performed on memory cells associated with the PECcluster 537-5 using a read level corresponding to the PEC cluster 537-6.However, the margin check is unsuccessful. As a result, a newcalibration cluster 535 is created and the PEC cluster 537-5, and groupsof memory cells associated therewith, are associated with thecalibration cluster 534. The calibration cluster 534 is the primarycalibration cluster because there are more PEC clusters associated withthe calibration cluster 534 than the calibration cluster 535.

Subsequently, a margin check is performed on memory cells associatedwith the PEC cluster 537-6 using a read level corresponding to the PECcluster 537-7. Because the margin check was successful, the PEC cluster537-6, and groups of memory cells associated therewith, are associatedwith the calibration cluster 535. Subsequently, a margin check isperformed on memory cells associated with the PEC cluster 537-7 using aread level corresponding to the PEC cluster 537-8. Because the margincheck was successful, the PEC cluster 537-7, and groups of memory cellsassociated therewith, are also associated with the calibration cluster535. Subsequently, a margin check is performed on memory cellsassociated with the PEC cluster 537-8 using a read level correspondingto the PEC cluster 537-9. Because the margin check was successful, thePEC cluster 537-8, and groups of memory cells associated therewith, arealso associated with the calibration cluster 535. The calibrationcluster 535 becomes the primary calibration cluster with the addition ofthe PEC cluster 537-8 because the calibration clusters 534 and 535 eachhave four PEC clusters associated therewith, but groups of memory cellsassociated with the PEC clusters 537-5, 537-6, 537-7, and 537-8 haveundergone greater quantities of PECs.

A margin check is performed on memory cells associated with the PECcluster 537-9 using a read level corresponding to the PEC cluster537-10. However, the margin check is unsuccessful. As a result, a newcalibration cluster 536 is created and the PEC cluster 537-9, and groupsof memory cells associated therewith, are associated with thecalibration cluster 536. Subsequently, a margin check is performed onmemory cells associated with the PEC cluster 537-10 using a read levelcorresponding to a different PEC cluster (not shown). Because the margincheck was successful, the PEC cluster 537-10, and groups of memory cellsassociated therewith, are associated with the calibration cluster 536.The calibration cluster 535 remains as the primary calibration clusterbecause there are more PEC clusters associated with the calibrationcluster 535 than the calibration cluster 536.

FIG. 7 illustrates an example of a system 748 including a computingsystem 700 in a vehicle 755 in accordance with some embodiments of thepresent disclosure. The computing system 700 can include a memorysub-system 704, which is illustrated as including a controller 706 andnon-volatile memory device 716 for simplicity but is analogous to thememory sub-system 104 illustrated in FIG. 1. The computing system 700,and thus the host 702, can be coupled to one or more sensors 744-1,744-2, 744-3, 744-4, 744-5, 744-6, 744-7, 744-8, . . . , 744-N eitherdirectly, as illustrated for the sensor 752-4 or via a transceiver 752as illustrated for the sensors 744-1, 744-2, and 744-3. The transceiver852 is able to receive time based telemetric sensor data from thesensors 744 wirelessly, such as by radio frequency communication. In atleast one embodiment, each of the sensors 744 can communicate with thecomputing system 700 wirelessly via the transceiver 744. In at least oneembodiment, each of the sensors 744 is connected directly to thecomputing system 700 (e.g., via wires or optical cables). As usedherein, telemetric sensor data means that the data is collected by thesensors 744 that are remote from the memory sub-system 704 that storesthe data (the receiving equipment). The telemetric sensor data is timebased because the data is correlated with time. The time correspondingto each data point can either be stored with the telemetric data orderivable therefrom based on some metric, such as a known start time forthe data and a data rate. The time can be useful in the playback of thesequences preceding an accident, for example.

The vehicle 755 can be a car (e.g., sedan, van, truck, etc.), aconnected vehicle (e.g., a vehicle that has a computing capability tocommunicate with an external server), an autonomous vehicle (e.g., avehicle with self-automation capabilities such as self-driving), adrone, a plane, a ship, and/or anything used for transporting peopleand/or goods. The sensors 744 are illustrated in FIG. 7 as includingexample attributes. For example, the sensors 744-1, 744-2, and 744-3 arecamera sensors collecting data from the front of the vehicle 755. Thesensors 744-4, 744-5, and 744-8 are microphone sensors collecting datafrom the from the front, middle, and back of the vehicle 755. Thesensors 744-7, 744-8, and 744-N are camera sensors collecting data fromthe back of the vehicle 755. As another example, the sensors 744-5 and744-6 are tire pressure sensors. As another example, the sensor 744-4 isa navigation sensor, such as a global positioning system (GPS) receiver.As another example, the sensor 744-6 is a speedometer. As anotherexample, the sensor 744-4 represents one or more engine sensors such asa temperature sensor, a pressure sensor, a voltmeter, an ammeter, atachometer, a fuel gauge, etc. As another example, the sensor 744-4represents a video camera.

The host 702 can execute instructions to provide an overall controlsystem and/or operating system for the vehicle 755. The host 702 can bea controller designed to assist in automation endeavors of the vehicle755. For example, the host 702 can be an advanced driver assistancesystem controller (ADAS). An ADAS can monitor data to prevent accidentsand provide warning of potentially unsafe situations. For example, theADAS can monitor sensors in the vehicle 755 and take control of vehicle755 operations to avoid accident or injury (e.g., to avoid accidents inthe case of an incapacitated user of a vehicle). The host 702 may needto act and make decisions quickly to avoid accidents. The memorysub-system 704 can store reference data in the non-volatile memorydevice 716 such that time based telemetric sensor data from the sensors744 can be compared to the reference data by the host 702 in order tomake quick decisions.

FIG. 8 is a block diagram of an example computer system in whichembodiments of the present disclosure can operate. Within the computersystem 890, a set of instructions, for causing a machine to perform oneor more of the methodologies discussed herein, can be executed. Thecomputer system 890 includes a processing device 892, a main memory 894,a static memory 898 (e.g., flash memory, static random access memory(SRAM), etc.), and a data storage system 899, which communicate witheach other via a bus 897. The data storage system 899 is analogous tothe memory sub-system 104 illustrated in FIG. 1.

The processing device 892 represents one or more general-purposeprocessing devices such as a microprocessor, a central processing unit,or the like. More particularly, the processing device can be a complexinstruction set computing (CISC) microprocessor, reduced instruction setcomputing (RISC) microprocessor, very long instruction word (VLIW)microprocessor, or a processor implementing other instruction sets, orprocessors implementing a combination of instruction sets. Theprocessing device 892 can also be one or more special-purpose processingdevices such as an ASIC, an FPGA, a digital signal processor (DSP),network processor, or the like. The processing device 892 is configuredto execute instructions 893 for performing the operations and stepsdiscussed herein. The computer system 890 can further include a networkinterface device 895 to communicate over a network 896.

The data storage system 899 can include a machine-readable storagemedium 891 (also known as a computer-readable medium) on which is storedone or more sets of instructions 893 or software embodying one or moreof the methodologies or functions described herein. The instructions 893can also reside, completely or at least partially, within the mainmemory 894 and/or within the processing device 892 during executionthereof by the computer system 890, the main memory 894 and theprocessing device 892 also constituting machine-readable storage media.

In some embodiments, the instructions 893 can be executed to implementfunctionality corresponding to the calibration circuitry 112 of FIG. 1.The instructions 893 can be executed to perform a media managementoperation on groups of memory cells of a memory device using respectiveread voltages. The respective read voltages can be based on a respectivequantity of PECs that each respective group of memory cells hasundergone. The instructions 893 can be executed to, responsive to aunsuccessful result of the media management operation, perform the mediamanagement operation on one or more of the groups of memory cells usingthe read voltage that yielded a last successful result of the mediamanagement operation, irrespective of a quantity of PECs undergone bythe one or more groups of memory cells.

In some embodiments, the instructions 893 can be executed to perform themedia management operation according to a sequence based on therespective quantities of PECs undergone by each respective group ofmemory cells. The instructions 893 can be executed to, responsive toanother unsuccessful result of the media management operation subsequentto the unsuccessful result, perform the media management operation onanother one of the groups of memory cells using the read voltage thatyielded a last successful result of the media management operation,irrespective of a quantity of PECs that the other group of memory cellshas undergone.

In some embodiments, the instructions 893 can be executed to perform themedia management operation on groups of memory cells of the memorydevice throughout a service life of the memory device. Magnitudes of theread voltages can be based on a remaining portion of the service life ofthe memory device.

While the machine-readable storage medium 891 is shown in an exampleembodiment to be a single medium, the term “machine-readable storagemedium” should be taken to include a single medium or multiple mediathat store the one or more sets of instructions. The term“machine-readable storage medium” shall also be taken to include amedium that is capable of storing or encoding a set of instructions forexecution by the machine and that cause the machine to perform one ormore of the methodologies of the present disclosure. The term“machine-readable storage medium” shall accordingly be taken to include,but not be limited to, solid-state memories, optical media, and magneticmedia.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. The presentdisclosure can refer to the action and processes of a computer system,or similar electronic computing device, that manipulates and transformsdata represented as physical (electronic) quantities within the computersystem's registers and memories into other data similarly represented asphysical quantities within the computer system memories or registers orother such information storage systems.

The present disclosure also relates to an apparatus for performing theoperations herein. This apparatus can be specially constructed for theintended purposes, or it can include a general purpose computerselectively activated or reconfigured by a computer program stored inthe computer. Such a computer program can be stored in a computerreadable storage medium, such as, but not limited to, types of diskincluding floppy disks, optical disks, CD-ROMs, and magnetic-opticaldisks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, or typeof media suitable for storing electronic instructions, each coupled to acomputer system bus.

The algorithms and displays presented herein are not inherently relatedto a particular computer or other apparatus. Various general purposesystems can be used with programs in accordance with the teachingsherein, or it can prove convenient to construct a more specializedapparatus to perform the method. The structure for a variety of thesesystems will appear as set forth in the description below. In addition,the present disclosure is not described with reference to a particularprogramming language. It will be appreciated that a variety ofprogramming languages can be used to implement the teachings of thedisclosure as described herein.

The present disclosure can be provided as a computer program product, orsoftware, that can include a machine-readable medium having storedthereon instructions, which can be used to program a computer system (orother electronic devices) to perform a process according to the presentdisclosure. A machine-readable medium includes a mechanism for storinginformation in a form readable by a machine (e.g., a computer). In someembodiments, a machine-readable (e.g., computer-readable) mediumincludes a machine (e.g., a computer) readable storage medium such as aROM, RAM, magnetic disk storage media, optical storage media, flashmemory devices, etc.

In the foregoing specification, embodiments of the disclosure have beendescribed with reference to specific example embodiments thereof. Itwill be evident that various modifications can be made thereto withoutdeparting from the broader spirit and scope of embodiments of thedisclosure as set forth in the following claims. The specification anddrawings are, accordingly, to be regarded in an illustrative senserather than a restrictive sense.

What is claimed is:
 1. A method, comprising: applying, to a memory cellof a first group of memory cells of a memory device, a signal associatedwith performance of a memory operation and having a first magnitude,wherein the memory cells of the first group have undergone respectivequantities of program/erase cycles (PECs) within a first range of PECsand the first magnitude corresponds to a second range of PECs differentthan the first range of PECs; determining, for the first group of memorycells: whether a first difference between a first target voltagecorresponding to a first data state and the signal having the firstmagnitude is at least a threshold value; and whether a second differencebetween a second target voltage corresponding to a second data state andthe applied signal having the first magnitude is at least the thresholdvalue; and responsive to determining that, for the first group of memorycells, the first and second differences are at least the thresholdvalue: associating the first group of memory cells with a firstcalibration cluster; and applying, to a memory cell of a second group ofmemory cells of the memory device, the signal having a second magnitude,wherein the memory cells of the second group have undergone respectivequantities of PECs within the second range of PECs and the secondmagnitude corresponds to a third range of PECs different than the secondrange of PECs.
 2. The method of claim 1, further comprising:determining, for the second group of memory cells: whether a thirddifference between a third target voltage corresponding to the firstdata state and the signal having the second magnitude is at least thethreshold value; and whether a fourth difference between a fourth targetvoltage corresponding to the second data state the signal having thefirst magnitude is at least the threshold value; and responsive todetermining that, for the second group of memory cells, the third andfourth differences are at least the threshold value, associating thesecond group of memory cells with the first calibration cluster.
 3. Themethod of claim 2, further comprising applying, to a memory cell of athird group of memory cells of the memory device, the signal having athird magnitude, wherein the memory cells of the third group haveundergone respective quantities of PECs within the third range of PECsand the third magnitude corresponds to a fourth range of PECs differentfrom the third range of PECs.
 4. The method of claim 1, furthercomprising, responsive to determining that the first difference or thesecond difference is less than the threshold value, associating thefirst group of memory cells with a second calibration cluster.
 5. Themethod of claim 4, further comprising, responsive to determining thatthe first difference or the second difference is less than the thresholdvalue: designating the second calibration cluster as a primarycalibration cluster; and applying, to a memory cell of a third group ofmemory cells of the memory device, the signal having the secondmagnitude, wherein the memory cells of the third group have undergonerespective quantities of PECs within the third range of PECs differentfrom the second range of PECs and the third magnitude corresponds to afourth range of PECs different from the third range of PECs.
 6. Themethod of claim 5, further comprising designating the second calibrationcluster as the primary calibration cluster in response to a greaterquantity of groups of memory cells of the memory device being associatedwith the second calibration cluster than the first calibration cluster.7. The method of claim 5, wherein a same quantity of groups of memorycells of the memory device is associated with the first and secondcalibration clusters, and wherein the method further comprisesdesignating the second calibration cluster as the primary calibrationcluster in response to groups of memory cells of the memory device thathave undergone greater quantities of PECs being associated with thesecond calibration cluster than the first calibration cluster.
 8. Themethod of claim 1, wherein determining whether the first difference isat least the threshold value comprises performing a first read operationon the first group of memory cells using a first read voltage less thanthe first magnitude; and wherein determining whether the seconddifference is at least the threshold value comprises performing a secondread operation on the first group of memory cells using a second readvoltage greater than the first magnitude.
 9. The method of claim 1,wherein determining whether the first and second differences are atleast the threshold value comprises performing two read operations onthe first group of memory cells using read voltages having magnitudesoffset from the first magnitude.
 10. A system, comprising: a processingdevice; and a memory device communicatively coupled to the processingdevice, wherein the processing device is to: perform, using a firstvoltage, a media management operation on a first group of memory cellsof the memory device that has undergone quantities of program/erasecycles (PECs) within a first range of PECs, wherein a magnitude of thefirst voltage corresponds to a second range of PECs exceeding the firstrange of PECs; responsive to a first result of the media managementoperation on the first group of memory cells, perform, using a secondvoltage, the media management operation on a second group of memorycells of the memory device that has undergone quantities of PECs withinthe second range of PECs, wherein a magnitude of the first voltagecorresponds to a third range of PECs exceeding the second range of PECs;and responsive to a second result of the media management operation onthe first group of memory cells, perform, using the first read voltage,the media management operation on the second group of memory cells. 11.The system of claim 10, wherein a boundary of the first range of PECs iszero PECs, and wherein the processing device is to: responsive to thefirst result of the media management operation on the second group ofmemory cells, perform, using a third voltage, the media managementoperation on a third group of memory cells of the memory device that hasundergone quantities of PECs within the third range of PECs, wherein amagnitude of the third voltage corresponds to a fourth range of PECsexceeding the third range of PECs; and responsive to the second resultof the media management operation on the second group of memory cells,perform, using the second read voltage, the media management operationthe third group of memory cells.
 12. The system of claim 11, wherein theprocessing device is to, subsequent to performance of the mediamanagement operation on at least one of the first, second, and thirdgroups of memory cells, perform, using a fourth voltage, the mediamanagement operation on a fourth group of memory cells of the memorydevice that has undergone quantities of PECs within the first range ofPECs.
 13. The system of claim 12, wherein the first voltage isassociated with a different trim than the fourth voltage.
 14. The systemof claim 10, wherein the memory device comprises a cyclic buffer portionand a snapshot portion comprising the first group of memory cells andthe second group of memory cells, and wherein the first range of PECs is0 to 10,000 PECs and at least one memory cell of the snapshot portionhas undergone greater than 90,000 PECs.
 15. The system of claim 14,wherein at least one memory cell of the snapshot portion that hasundergone fewer than 10,000 PECs is programmed using a first trim, andwherein at least one memory cell of the snapshot portion that hasundergone greater than 90,000 PECs is programmed using a second trim.16. The system of claim 10, wherein the system comprises a solid statedrive to provide event recorder storage for an autonomous vehicle.
 17. Anon-transitory computer-readable storage medium comprising instructionsthat, when executed by a processing device, cause the processing deviceto: perform a media management operation on groups of memory cells of amemory device using respective read voltages based at least in part on arespective quantity of program/erase cycles (PECs) that each respectivegroup of memory cells has undergone; and responsive to a firstunsuccessful result of the media management operation, perform the mediamanagement operation on at least one of the groups of memory cells usingthe read voltage that yielded a last successful result of the mediamanagement operation irrespective of a quantity of PECs that the atleast one group of memory cells has undergone.
 18. The medium of claim17, further comprising instructions to perform the media managementoperation according to a sequence based at least in part on therespective quantities of PECs undergone by each respective group ofmemory cells.
 19. The medium of claim 17, further comprisinginstructions to, responsive to a second unsuccessful result of the mediamanagement operation subsequent to the first unsuccessful result,perform the media management operation on another one of the groups ofmemory cells using the read voltage that yielded a last successfulresult of the media management operation irrespective of a quantity ofPECs that the other group of memory cells has undergone.
 20. The mediumof claim 17, further comprising instructions to perform the mediamanagement operation on groups of memory cells of the memory devicethroughout a service life of the memory device, wherein magnitudes ofthe read voltages are based at least in part on a remaining portion ofthe service life of the memory device.